I have this lens also, and have no problems on both my t2i and 5DM3 with viewfinder autofocus - it's right on, with no AFMA needed. It is a little noisy focusing compared to my other lenses, but the image quality is outstanding - probably the sharpest lens I own. It does, however, have problems with LiveView autofocus for some reason on the 5DM3, but not on the t2i. I have the same issue with my Sigma 150 macro - great image quality, no problems with viewfinder AF, but hunts and sometimes misses with Liveview AF.

The AF hit rate is good! A get a higher percentage of sharp shots than with the 50mm 1.4 both at 2.8It is super sharp wide open!Focus is a bit noisy but I would call it fast in a portrait situation. In a macro situation it gets slower and at 1:2 I switch to MF most of the time. Beware that it extends quite a bit.